Sequential decoupling of negative-energy states in Douglas-Kroll-Hess theory

Here, we review the historical development, current status, and prospects of Douglas--Kroll--Hess theory as a quantum chemical relativistic electrons-only theory.Comment: 15 page

Theory of Laser-Enhanced Ionization in Flames - Comparison with Experiments

La spectroscopie optogalvanique ou par augmentation de l'ionisation à l'aide d'un laser (L.E.I.) a été mise en oeuvre pour la détection d'éléments à l'état de traces dans une flamme par excitation à un et deux échelons. La sensibilité, définie comme étant le signal L.E.I. divisé par l'énergie de l'impulsion lumineuse et par la concentration des éléments en solution dans l'eau aspirés dans la flamme, a été mesurée pour plusieurs atomes. Un modèle théorique pour le processus d'accroissemnt de l'ionisation par excitation laser a été développé et comparé aux résultats expérimentaux. Cette comparaison montre l'importance des niveaux d'énergie qui ne sont pas impliqués directement dans les excitations lasers. L'accord entre théorie et expérience est satisfaisant. Quelques explications possibles sont proposées et discutées à propos des points de désaccord.Opto-galvanic or laser-enhanced ionization (LEI) spectroscopy has been performed on trace elements in a flame using one- and two-step laser excitations. The sensitivity, defined as the LEI signal divided by the laser pulse energy and the concentration of the trace element in the water solution aspirated into the flame, has been measured for a number of elements. A theoretical model for the LEI process has been developed and tested. The importance of energy levels, not involved in the laser transitions, is emphasized. The agreement between theory and experiment is satisfactory. Possible reasons for discrepancies which arise are discussed

The GAMESS-UK electronic structure package: algorithms, developments and applications.

NoA description of the ab initio quantum chemistry package GAMESS-UK is presented. The package offers a wide range of quantum mechanical wavefunctions, capable of treating systems ranging from closed-shell molecules through to the species involved in complex reaction mechanisms. The availability of a wide variety of correlation methods provides the necessary functionality to tackle a number of chemically important tasks, ranging from geometry optimization and transition-state location to the treatment of solvation effects and the prediction of excited state spectra. With the availability of relativistic ECPs and the development of ZORA, such calculations may be performed on the entire Periodic Table, including the lanthanides. Emphasis is given to the DFT module, which has been extensively developed in recent years, and a number of other, novel features of the program. The parallelization strategy used in the program is outlined, and detailed speedup results are given. Applications of the code in the areas of enzyme and zeolite catalysis and in spectroscopy are described